1. Field of the Invention
The present invention relates to a hardness tester and a program.
2. Description of Related Art
Conventionally, a testing method is known called instrumented indentation testing (nanoindentation) in which a test force (force with which a load is placed on an indenter) and a pressing depth (amount of displacement of the indenter) are continuously measured during a process where a predetermined load is placed on the indenter to press the indenter into a surface of a sample and form an indentation. A pressing curve obtained from the measurements is then analyzed to find mechanical characteristics of a material.
In general, in instrumented indentation testing, a uniform test force is applied to the indenter, which approaches the sample at a uniform speed. A point is then detected where the displacement amount changes or the speed of the indenter changes when the indenter makes contact with the sample. The test is begun with that point serving as a surface of the sample (zero point). Therefore, accuracy in detection of the point where the indenter contacts the sample (zero point) influences precision of test results for the instrumented indentation testing. Thus, a variety of innovations have been conventionally employed as a method for detecting the zero point. For example, Japanese Patent Publication No. 3731047 discloses a technique for detecting a point where an indenter contacts a sample by sending micro-vibrations through the indenter, then approaching the indenter toward the sample and detecting a change in the vibrations. Alternatively, Japanese Patent Publication No. 3839512 discloses a technique for determining the zero point by obtaining load data and displacement data before the indenter touches the sample, then detecting changes in the approach of the indenter either after contact or after testing.